The Danger of Backflow
Safe drinking water is so commonly available in this nation that we take it for granted that any water we consume from our faucet is safe to drink. The Berkeley County Public Service Water District (BCPSWD) works hard to insure that the water we deliver to our customers meets or exceeds health standards. However, a potential threat to your drinking water exists. The threat is backflow, or a cross-connection which can turn a pure glass of drinking water into a lethal brew.
Here's How it Works. Say you are watering your garden with a fertilizer or pesticide applicator attached to your hose. The phone rings, and you leave the garden. While you are chatting, there is a pressure fluctuation in our system that causes a vacuum. Like a straw, the vacuum will pull your pesticide-laced water into public water supply. The next time you or your neighbors turn on a faucet, the water could be laced with the pesticides. Backflow is not just a theoretical possibility. There are many documented cases of this happening.
Eliminating The Threat. We can substantially reduce this threat to our drinking water by installing a backflow preventer which allows water to pass through it in only one direction. The Federal Safe Drinking Water Act on 1974 requires that we provide water that is safe for consumption and free from contaminants. The BCPSWD also requires these backflow preventers on water lines serving our industrial and commercial users. Although residential customers pose the greatest probability of backflow, commercial customers pose the greatest hazard to our water supply. Therefore backflow preventers are required for all customers to make this layer of protection successful. It only takes one home without one of these devices to pollute the water supply.
Thermal Expansion
Once we install a backflow preventer on your water service line, water will be unable to flow back into the public water supply. The backflow preventer creates an isolated or closed plumbing system. For some homeowners, this could produce leaky faucets or set off the temperature and pressure relief valve on hot water heaters.
Why does this happen ? The culprit is Thermal Expansion. Before the backflow preventer was in place, water was forced back out to our public water supply by means of the hot water heater. Let me explain, as water was heated, it increased in volume and pressure forcing it back out to the water main, thus we get the term "thermal expansion." Once a backflow preventer is installed, the water can no longer expand in this direction and a plumbing system that is not up to current code could experience the conditions mentioned above. If your plumbing system is faulty, it could fail once the system is closed. For example, if thermal expansion exerted itself and the hot water heater relief valve was stuck, the hot water heater could develop a leak.
